The CACTI cohort is being followed for progression of coronary artery calcification (CAC) for development of clinical CVD and participants have been characterized during the baseline examination (4/00-3/02) and two follow-up re-examinations 3 and 6 years later. We are proposing assess a subset of this population to determine vasodilatory reserve as it relates to early coronary atherosclerosis in T1D. In the CACTI Study sought to determine the relationship between risk factors for CAD and coronary arterial calcification in T1D subjects compared to an age and gender matched control cohort. The trial identified CAC as a high risk marker of CAD and was more extensive in diabetic patients.